1. Field of the Invention
This invention concerns the use of a synergistic combination of a rust inhibitor containing at least one COOH group and particular derivatives of pyridine.
2. Description of Related Art
Many lubricating oils require the presence of rust inhibitors to inhibit or prevent rust formation, which often occurs due to water contacting a metal surface. However, we have found that the oil/water interfacial tension decreases with increasing concentration of the rust inhibitor. Therefore, although rust inhibition is improved, the demulsibility of the lubricating oil is degraded. Accordingly, it would be desirable to have a simple yet convenient means to obtain effective rust inhibition while reducing any adverse effect on the demulsibility of the oil.